Ye Fang, Brauer Tanja, Niehus Eike, Drlica Karl, Josenhans Christine, Suerbaum Sebastian
Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Carl-Neuberg-Strasse 1, D-30625 Hanover, Germany.
Int J Med Microbiol. 2007 Apr;297(2):65-81. doi: 10.1016/j.ijmm.2006.11.006. Epub 2007 Feb 1.
In Helicobacter pylori, a host-adapted bacterium with a small genome and few dedicated transcriptional regulators, promoter structure, and gene organization suggested a role for DNA topology in the transcriptional regulation of flagellar genes. H. pylori DNA supercoiling, monitored by a reporter plasmid, was relaxed by novobiocin, an inhibitor of DNA gyrase. A decrease in negative supercoiling coincided with lowered transcription of the late flagellin gene flaA. Targeted mutagenesis that either increased or decreased promoter spacer length in the flaA sigma(28) promoter lowered flaA transcript levels, expression of FlaA protein, and flagella formation. It also changed the promoter response to decreased superhelicity. Supercoiling of reporter plasmid DNA in H. pylori varied with growth phase in liquid culture. H. pylori sigma(28) promoters of various spacer length, as well as other supercoiling-sensitive genes, were differentially transcribed during the growth phases, consistent with supercoiling being associated with growth phase regulation. Genome-wide transcript analysis of wild-type H. pylori under conditions of reduced supercoiling identified flagellar, housekeeping, and virulence genes, the expression of which correlated with supercoiling change and/or growth phase. These data indicate that global supercoiling changes may help coordinate temporal (growth phase-related) regulation of flagellar biosynthesis and other cellular functions in Helicobacter.
幽门螺杆菌是一种适应宿主的细菌，基因组小且专一性转录调节因子少，其启动子结构和基因组织表明DNA拓扑结构在鞭毛基因转录调控中发挥作用。通过报告质粒监测发现，DNA旋转酶抑制剂新生霉素可使幽门螺杆菌的DNA超螺旋松弛。负超螺旋减少与晚期鞭毛蛋白基因flaA转录降低同时发生。在flaA σ(28)启动子中，靶向诱变增加或减少启动子间隔区长度会降低flaA转录水平、FlaA蛋白表达及鞭毛形成。这也改变了启动子对超螺旋减少的反应。在液体培养中，幽门螺杆菌报告质粒DNA的超螺旋随生长阶段而变化。不同间隔区长度的幽门螺杆菌σ(28)启动子以及其他超螺旋敏感基因在生长阶段转录存在差异，这与超螺旋与生长阶段调节相关一致。在超螺旋减少的条件下，对野生型幽门螺杆菌进行全基因组转录分析，确定了鞭毛、管家和毒力基因，其表达与超螺旋变化和/或生长阶段相关。这些数据表明，整体超螺旋变化可能有助于协调幽门螺杆菌中鞭毛生物合成和其他细胞功能的时间（与生长阶段相关）调节。
